1. Field of the Invention
The present invention relates to an image-pickup apparatuses, such as a digital camera and a video camera, configured to capture a motion image.
2. Description of the Related Art
It is known that a dynamic range (which is a ratio between the minimum brightness and the maximum brightness by which the gradation can be identified) of a solid-state image sensor, such as a CCD or CMOS image sensor is generally narrower than that of the human eye (FIG. 10).
It is thus difficult to reproduce the gradation actually perceived by the human eye in a picture. One known solution for this problem is a method for superimposing a plurality of images captured with different exposure conditions (such as an H image of a bright overexposure, an M image of a proper exposure, and an L image of a dark underexposure) for a high dynamic range (“HDR” hereinafter) wider than usual imaging (see, for example, Japanese Patent Laid-Open No. (“JP”) H06-141229).
FIG. 11 illustrates one illustrative photography for the HDR disclosed in JP H06-141229. A plurality of images (which are three images containing an H image, an M image, and an L image) are captured with different exposure conditions after the photography starts. Then, these images are synthesized for the HDR that contains an exposure difference between the H image and the L image.
JP H06-141229 discloses a method for creating an exposure difference utilizing the exposure time period. Hence, this method is unsuitable for the motion image photography in which an image is captured for each predetermined period (such as 30 fps) which means that 30 images are captured per second.